Sheet metal hot top and method of using exothermic material in pouring ingots



Nov. 24, 1959 w M. FARNSWORTH ETAL 2,913,736

SHEET METAL HOT TOP AND METHOD OF USING EXOTHERMIC MATERIAL IN POURINGINGOTS INVENTORS WALTER M. FAK/VSWUKTH Filed April 5, 1956 JACK h.KENNEDY SHEET METAL HOT TOP AND METHOD OF USING EXOTHERMIC MATERIAL INPOURING HIGOTS United States Patent Walter M. Farusworth, Canton, andJack H. Kennedy,

Waynesburg, Ohio, assignors to Republic Steel Corporation, Cleveland,Ohio, a corporation of New Jersey This invention relates to a method andapparatus for maintaining the metal in the upper part of an ingot moldin molten state after the pouring of the ingot.

As an ingot of metal, such as a steel ingot, cools in the mold andsolidifies, it shrinks and generally forms a cavity known as a pipe inthecenter of the ingot. Various methods and apparatus have been employedin an effort to avoid damage to the ingot by formation of this pipe. Afrequent device for eliminating such a pipe has been the use of a hottop. Hot tops, in general use, have a refractory lining or are made of arefractory material. The hot tops are placed on top of the ingot mold asan extension of the mold. As the molten metal solidifies in the ingot,and tends to form the central cavity, the metal in the hot top acts as areservoir to feed the metal into the cavity thus producing a soundingot. However, when the ingot is subsequently rolled to produced plateor sheet, the portion of the ingot which has remained in the hot top iscut off below the junction of the hot top and the ingot and the hot topportion of the metal is scrapped. The hot top section may constitutefrom ten percent to twenty percent of the ingot and usually runs betweentwelve percent and fourteen percent of the ingot.

In the use of the hot top, it is a conventional practice right after theingot is poured to cover the molten metal in the hot top with aninsulating material or an exothermic material which upon contact withthe metal reacts to maintain the adjacent metal in molten state. Theexothermic materials have been found to keep the metal in the moltenstate longer, and, therefore, usually permit a lower hot top volume,thus providing a better ingot yield, i.e., the amount of scrap metal inthe hot top section is reduced.

Some producers of high alloy steels have used electric arcs and gasheated hot tops to keep the metal molten during the solidifying of theingot, because in some cases the exothermic materials have been found tocontaminate the steel ingot, especially righ alloyed types, such asstainless steel.

' Therefore, although the exothermic materials have been found usefulfor maintaining high temperature during the solidifying of ingots, thecontamination of the ingots by the reaction products of the exothermicmaterials has been a deterrent to their use.

It is an important object of this invention to provide for a betteringot yield and also obtain ingots which are not contaminated by thereaction products of the exothermic materials and which do not requirethe equipment expense and other expense of keeping the metal molten atthe top of the mold by electric are or gas heating equipment.

Other important objects of the invention will be apparent from adescription of the invention.

' The invention comprises maintaining a mass of exothermic material inthe upper part of the mold out of Contact with,'but in heatconductiverelationship to the sheet metal, e.g. 28-gauge steel.

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metal, whereby the metal is maintained in molten state after the ingothas been poured and during the solidi fying and shrinking of the ingot.

The invention contemplates the use of an apparatus comprising acontainer extending into the mold from the top thereof, the containerbeing formed of heat conducting material and being filled with a mass ofexothermic material which reacts by contact of the molten metal with thewalls of the container. It is contemplated that the container in oneform will be in the shape of an annular collar fitting closely againstthe inner walls of the ingot mold and extending down into the mold fromthe upper end thereof.

-It is also contemplated that means will be provided on the containerfor supporting and maintaining it in position in the upper part of themold, the container being readily positioned in the upper part of themold prior to the pouring of the ingot, the container defining a centralopening through which metal may be poured into the mold while thecontainer is in place in the upper part thereof.

For a more complete description of the invention, reference is made tothe drawings wherein:

Fig. 1 is a cross-section of the upper part of an ingot mold withapparatus embodying this invention'disposed in the upper part of themold;

Fig. 2 is a plan view of the form of apparatus shown in Fig. 1;

Fig. 3 is a sectional view taken along the line 33 inFig. 2;'and

Fig. 4 is a cross-section of an ingot mold showing another form of theapparatus of this invention in position in the upper part of a mold.

Referring to Fig. 1, an ingot mold 10 for receiving molten metal isprovided with an inner wall 11 and top portion 12, the molten metalbeing received through the opening 13 in the top of the mold. Disposedin the upper part of the mold adjacent the top 12, is a container 15comprising an outer wall 16 which is of a size to fit within the upperpart of the ingotmold and adja cent the inner wall 11 of the mold. Thecontainer form a chamber 20 for receiving a mass of exothermic material.

The container is provided With brackets 22, suitably attached to theouter wall 16 to support it on the upper edge 12 of the mold, asindicated in Fig. l.

The bottom wall 18 may slope upwardly from the outer wall 16 to theinner wall 17, as best shown in Fig. '1. The walls of the container maybe made of suitable heat conductive material, such as metal, and forpractical purposes, may be made of relatively thin Where the metal ofthe ingot is an ordinary steel or is stainless or other highly alloyedsteel, it appears satisfactory to make the container 15 of ordinarysteel or iron. The metal container can be fabricated by welding or canbe stamped from sheet metal and the shape of the container may vary asdesired. For example, the bottom of the container may be rounded or thecontainer may take a generally V-shape, such as that shown in Fig. 4.

In Fig. 4, the outer wall 26 of the container 27 fits closely againstthe inner wall 28 of the ingot mold 30.

fit snugly in molds of any shape, e.g. square, round, corrugated, orgenerally rectangular as shown in Fig. 2.

Prior to the pouring of an ingot into the mold 10, the container 15 ispositioned as shown in Fig. 1 in the upper part of the ingot mold.

The molten metal is poured through the opening defined by the inner wall17 of the container into the ingot chamber 14 of the mold. As the moldis filled to the top with molten metal, the exothermic material in thecontainer reacts to generate a high temperature and maintain the metalin a molten state while the ingot below the container is solidifying.

Exothermic material starts to ignite within a few seconds after the hottop section is completely filled. Such materials ignite at about 700 F.To prevent too rapid reaction the exothermic material in the containermay be covered with a thin layer of dry sand or some other insulatingmaterial. In order to avoid contamination of the metal after the mold isfilled, it may be desirable, also, to cover the upper surface of themolten metal bounded by the inner wall 17 with a suitable insulatingmaterial, such as the layer of sand 25 shown in Fig. 4. A secondcovering of exothermic material may then be added with no ill effects.

The exothermic material used to fill the container may be of anysuitable type which is now available. One type which has been foundsatisfactory contains (i.e. analyzes) 08% C, .45% MnO .087% P, .0ll% S,3.75% SiO .l8% TiO 22.6% A1, 54.0% Fe O The analysis of another suitableexothermic material was as follows: .42% free C, 1.24% organic C, .19%MnO, .09% P 01% S, 48.7% SiO .04% N, .04% Cr O .l7% TiO 25.6% Al, 1.16%Cu, 6.90% Fe O .70% Fe, 1.6% A1 0, 1.19% G10, .76% MgO, 10.70% NaNO Athird example of a satisfactory exothermic material had the followinganalysis: 27.80% SiO 22.70% A1 0 2.88% F3203, 24.53% metallic Al, 3.07%NaNO .to% metallic Mg, 7.34% MnO. The grades or types of exothermicmaterial which have been found suitable generally contain amounts ofaluminum and iron oxide as the principal reactants. Sodium nitrate isalso used, and in some cases barium nitrate is used to replace sodiumnitrate with the result that there is less smoke.

The exothermic temperatures have been found to reach approximately 4,300F. Although there is some tendency for the container walls to break downunder these extreme temperatures, the general effect is that thecontainer walls are sufiiciently effective during the exothermicreaction to maintain the exothermic material out of direct contact withthe molten metal, and prevent contamination of the ingots. After thereaction subsides, a white hot layer of residue is formed which keepsthe metal in a molten state for an extended period. The time forcomplete solidification is extended by 20% over that when a conventionalrefractory hot top is used.

It has been found that exothermic and refractory materials, if notprotected, will pick up moisture when stored for a period of time, and,therefore, previously when hot tops have been used with refractoryliners or when exothermic material has been employed with such hot tops,the moisture in such materials has been released into the molten metaland the steam generated thereby has caused further damage to the ingot.With the employment of the container of this invention for theexothermic material, the molten metal is protected from the moisturewhich would normally be picked up by the exothermic materials, for infilling the container, it has been found that the exothermic materialcan be tamped into the container and thereafter allowed to dry so as toform a hard solid mass freed of a substantial part of its moisture. Theexothermic material in the container is thereafter protected frompicking up further moisture during the period it is stored in thecontainer awaiting use in an ingot mold. One practical method of dryingthe exothermic material after it has been loaded into the container isby heating 4 gently until the material is substantially free of moistureand is formed into a hard solid mass.

Although it is preferred to have containers in the form shown whichachieve good results without extending above the top of the mold, it isentirely within the scope of this invention to have the walls of thecontainer extend above the level of the mold top, although it isdesirable to have the container with the exothermic material extend alittle way into the mold, eg at least two inches into the mold.

It has been found that by the use of the method and apparatus of thisinvention, it has been possible to increase the efiiciency in thepouring of ingots because the volume of metal needed to fill the area inthe mold within the inner walls of the container is about one-half orless than that required in the present hot tops and that the use of thecontainers is much easier than the use of hot tops because thecontainers are lighter and easier to handle when placing on the mold,the molten metal is not contaminated by exothermic materials in directcontact with the metal, and, as noted above, the metal is protected frommoisture from refractory or exothermic materials in contact with themetal. All these advantages have been achieved by the use of thisinvention and have resulted in a more efficient production of soundingots with a reduction of the amount of scrapping of the upper end ofthe ingot.

In cases in which it is desirable to have the ingot extend above themold so that it may be used as a tong hold for stripping of the ingotfrom the mold, a conventional refractory hot top may be used as anextension to the mold and the metal container filled with exothermicmaterial may be placed in position inside the refractory hot top.

In accordance with the provisions of the patent statutes, I have hereindescribed the principle of operation of the invention, together with theelements which I now consider the best embodiments thereof, but I desireto have it understood that the structure disclosed is only illustrativeand the invention can be carried out by other means. Also, while it isdesigned to use the various features and elements in the combinationsand relations described, some of these may be altered and modifiedwithout interfering with the more general results outlined.

Having thus described our invention, we claim:

In the combination of an ingot mold having an upwardly opening uprightinterior cavity into which molten steel is to be poured for casting aningot, and a hot top structure for said mold comprising an annular sheetmetal container having a central opening and arranged to be disposed forreceiving the uppermost portion of the steel poured through said openingto fill the mold and the opening, said container being a unitarystructure which has inner and outer walls of thin ferrous metal sheetand which provides a vertically extending annular recess between itsinner and outer walls, to surround the central opening, the improvementwhich comprises said container having its outer wall shaped to fitclosely within said cavity of the ingot mold, said container beingpositioned substantially Wholly within the mold, below and immediatelyadjacent the top of the mold, and said improvement further comprising,in combination, a mass of self-reactmg exothermic material contained inand held by said recess of the container and disposed in abutment withthe inner wall around the central opening, in substantially encasingrelation to said opening, said material being separated from theinterior of the mold, at said opening, only by said thin ferrous metalof the container, said container being proportioned to hold, within itscentral opening, less than 10% of the total steel poured to fill thespace which consists of said opening and the mold cavity below thecontainer, and said container and said exothermic material beingconstructed and arranged to prolong, after pouring, the molten state ofthe poured steel ad jacent the top of the mold and to preventcontaminating 5 access of the reacted residue of the exothermic material1,654,057 to the molten steel in the mold. 2,229,045 2,261,289References Cited in the file of this patent 2,237,073

UNITED STATES PATENTS 5 1,192,617 Gathmann July 25, 1916 218,4451,294,209 Walker Feb. 11, 1919 524,383 1,498,323 La Cour June 17, 1924653,717 1,553,019 Bate Sept. 8, 1925 10 119,418

6 Smith Jan. 13, 1927 Cadwell Jan. 21, 1941 Rowe Nov. 4, 1941 Udy June23, 1942 FOREIGN PATENTS Great Britain July 10, 1924 Great Britain Aug.6, 1940 Great Britain May 23, 1951 Australia Jan. 5, 1945

